governmentchemist


New drink-drive limits in Scotland by Nick Boley
December 8, 2014, 10:26
Filed under: transport, UK Government Information | Tags: , ,

The Scottish Government have introduced a lower alcohol limit for drivers on 5 December (SSI 328/2014). This differentiates Scotland from the rest of the United Kingdom in that the legal maximum alcohol level in blood has fallen, for blood,  from 80 mg per 100 mL to 50 mg per 100 mL, for urine from 107 mg per 100 mL to 67 mg per 100 mL, and for breath from 35 µg per 100 mL to 22 µg per 100 mL.

This brings Scotland into line with a significant number of EU countries. In order to enforce this new legislation, forensic laboratories will need to amend their measurement methods in order to accurately determine, with a known uncertainty of measurement, alcohol in blood and urine at these new , lower, levels. This will not present any challenges, and certified reference materials (CRMs) containing alcohol at these levels to support these measurements are already widely available. Roadside testing equipment used by Police Scotland must also be ale to cope with these changes, and CRMs are also widely available at the lower levels to calibrate and validate the equipment used, for example from LGC Standards.

A specific concern to may in Scotland now is the “morning-after” effect, when alcohol level residues from the previous day could render drivers over the new limit where they would not have been previously. Some companies have been marketing products for use by drivers to check their status in the morning, such as Alcosense™, specifically aimed at Scotland and the new lower level. These check the breath alcohol level, convert to blood alcohol level, and are for guidance. They have no legal status. The principle on which these devices work is similar to the roadside devices used by the police. They have been shown to have high precision, i.e. they are consistent. However, no data has ever been produced to demonstrate their absolute accuracy although anecdotally they appear to give expected results based on intake. The accuracy claims of manufacturers need to be understood by the user. Accuracy to 0.2 % blood alcohol level (equivalent to 20 mg per 100 mL blood) may look very impressive, but for the new Scottish law equates to a relative potential error of ± 40 %. So, if it reads 0.3 % you may be OK, you may not. If it reads 0.7 % you are probably not OK, but on the other hand you may be just OK. This has the effect of building in a safety margin, but the interpretation of the data, as with any handheld device for personal measurement of anything (e.g. cholesterol, blood sugar), is key and the responsibility ultimately lies with the user.

 

 

 

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